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Plant sterols (PS) are effective in reducing plasma lipid concentrations, however, few studies have examined their cholesterol lowering effects in type 2 diabetics. The objective was to assess whether PS consumption alters blood lipid profile in hypercholesterolemic subjects with and without type 2 diabetes. Fifteen control subjects (age = 55.1 +/- 8.5 yr and BMI = 26.9 +/- 3.0kg/m2) and fourteen diabetic subjects (age = 54.5 +/- 6.7 yr and BMI = 30.2 +/- 3.0kg/m2) participated in a double-blinded, randomized, crossover, placebo-controlled feeding trial. The Western diet included either 1.8g/d of PS or cornstarch placebo each provided over 21 d separated by a 28 d washout period. Subjects consumed only foods prepared in Mary Emily Clinical Nutrition Research Unit of McGill University. Total cholesterol (TC) decreased (p < 0.05) from baseline with PS for control and diabetic subjects by 9.7% and 13.6%, respectively. TC decreased (P < 0.05) from baseline with placebo for control and diabetic subjects by 10.9% and 11.6%, respectively. Non high density lipoprotein cholesterol (non-HDL-C) decreased (p < 0.05) from baseline with PS for diabetic subjects by 18.5%. Low density lipoprotein cholesterol (LDL-C) levels were reduced (p < 0.05) from baseline with PS for control and diabetic subjects by 14.9% and 29.8%, respectively. The reduction of LDL-C due to PS alone is greater with type 2 diabetics. There were no significant changes in HDL-C and TG across diets or treatments. It is thus concluded that PS consumption with diet enhances non-HDL-C and LDL-C reduction compared with diet alone in hypercholesterolemic individuals with and without type 2 diabetes. Demonstration for the first time that PS alone are more efficacious in lowering LDL-C and non-HDL-C in diabetic individuals compared to non-diabetics confirm the beneficial effects of PS to help prevent cardiovascular disease (CVD) for this high risk population.

The objective of this research was to examine the effects of plant sterols and glucomannan on lipid profiles, plasma plant sterol levels and glycemic control in mildly hypercholesterolemic subjects. Thirteen type 2 diabetic and sixteen non-diabetic individuals participated in a randomized crossover trial consisting of 4 phases, of 21 days each. During the study period, subjects were supplemented with plant sterols and/or glucomannan. Overall reductions of total cholesterol and low-density lipoprotein (LDL) cholesterol concentrations were greater after consumption of plant sterols and glucomannan compared to plant sterol or glucomannan supplementation alone. Plasma lathosterol levels, indicators of cholesterol biosynthesis, were decreased after combination treatment. The results suggest that a combination of glucomannan and plant sterols substantially improve plasma lipids by reducing cholesterol absorption and synthesis simultaneously. Supplementation of plant sterols and glucomannan can thus be used as an effective treatment for management of circulating cholesterol levels and prevention of cardiovascular disease.

The objective of this study was to compare the effect of phytosterols (PS) on lipid profiles and cholesterol kinetics of hypercholesterolemic individuals with or without type 2 diabetes. It was hypothesised that the response to PS would differ between both groups due to different lipid metabolism. During this randomised, double blind, crossover trial, participants consumed a controlled diet with placebo or PS for 21 days. / Plasma total cholesterol (TC) decreased with placebo and PS (10.9% and 9.7% in non-diabetic versus 11.6% and 13.6% in diabetic participants, p < 0.05). Plasma low-density lipoprotein cholesterol (LDL) significantly decreased with PS in both groups. The reduction in LDL with PS was greater in diabetic compared to non-diabetic individuals (29.8% versus 14.9%, p < 0.05). Cholesterol absorption decreased on average (p = 0.06) by 26.5% with PS compared with placebo in the diabetic group only. Therefore, a controlled heart healthy diet reduced TC and LDL concentrations in non-diabetic and diabetic individuals. Adding PS as adjuncts to a hypocholesterolemic dietary treatment was associated with lower LDL concentrations and cholesterol absorption in hypercholesterolemic participants with type 2 diabetes.

The current study examined the impact of plant sterols, stanols, sterol esters, and stanol esters on (i) cholesterol-lowering efficiency, (ii) gene expression of ABCG5 and ABCG8 sterol transporters in the liver and small intestine, and (iii) colon mucosal cell proliferation in hamsters. After 5 weeks on experimental diets, plasma total cholesterol levels were reduced ( P<0.05) by stanols, sterol esters and stanol esters compared to cholesterol-control diet. Different PS analogs did not alter ABCG5 and ABCG8 mRNA levels in small intestine and liver as compared to cholesterol control. In addition, colon mucosal cell proliferation was 21.4% lower (P<0.01) in group fed 0.7% stanol esters relative to cholesterol control. Results suggest that hypocholesterolemic effects of PS analogs are not associated with changes of liver and small intestine ABCG5 and ABCG8 sterol transporters. Data also indicated that plant stanol ester may possess anticarcinogenic properties.

The objective of this study was to examine the effects of plant sterols and/or glucomannan on lipid profiles and cholesterol kinetics in hyperlipidemic individuals with or without type 2 diabetes. It was hypothesized that plant sterols and glucomannan reduce circulating cholesterol levels and may have an additive or synergistic effect when combined by reducing cholesterol absorption. Thirteen type 2 diabetics and sixteen non-diabetics all mildly hypercholesterolemic free living subjects participated in a randomized crossover trial consisting of 4 phases, 21 days each. Subjects consumed plant sterols and glucomannan during the trial. Overall reductions in total and LDL-cholesterol levels were greater (P<0.05) after consumption of the combination supplement. Effects of supplements were not different between diabetics and non-diabetics. No significant changes were observed in cholesterol absorption or synthesis in both diabetics and non-diabetics. The intake of plant sterols and glucomannan together may be an alternative approach in reducing blood cholesterol levels.

Statins are widely used to treat hypercholesterolemia. Statins inhibit cholesterol biosynthesis, thereby activating genes involved in cholesterol homeostasis, which are under the control of the Sterol Regulatory Element (SRE). Statins also have cholesterol-independent beneficial cardiovascular effects mediated through the phosphoinositide 3-kinase (PI3-K) / Akt signaling pathway and by inhibition of protein prenylation. Because statins inhibit the synthesis of isoprenoids, they can act by inhibiting the small signaling GTPases Ras and Rho, which require post-translational prenylation to become membrane-anchored and functional. We showed that simvastatin-mediated inhibition of protein prenylation does not appear to play a role in activation of SRE transcriptional activity in HepG2 cells. We also found that when isoprenoids were replenished, basal phospho-Akt decreased, suggesting that inhibition of prenylation by simvastatin mediates Akt phosphorylation. Future studies will be needed to investigate the role that inhibition of protein prenylation plays in the activation of the PI3-K/Akt pathway by simvastatin. / Department of Biology

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